Excerpt:
If “forever” can seem to work as a translation, why quibble about it? The problem is there are also dozens of verses where this translation would be nonsensical. Consider, for example, when the resurrected Jesus gave encouragement to his disciples on a mountain in Galilee: “and, lo, I am with you alway, even unto the end of the world [aiōnos]” (Matt 28:20; KJV). Clearly, this couldn’t be translated as “unto the end of the forever”, or “unto the end of the eternity”. So, what is going on with the original Greek? The Greek closes ἕωςτῆς συντελείας τοῦ αἰῶνος, which translates more literally as “until the completion of the age [aiōnos]”. Yet here, the KJV suddenly chooses “world”.
It does so in many other instances where “forever” would be clearly unsuitable. Consider Paul’s Epistle to the Romans, where he warns the fledgling church “be not conformed to this world” (Rom 12:2; KJV). The Greek here is μὴ συσχηματίζεσθε τῷ αἰῶνι, quite literally “be not conformed to the age [aiōni]”. Clearly, “be not conformed to this forever” or “be not conformed to this eternity” would make no sense. And so the KJV and many other major English-language bibles, which translate aion as “forever” elsewhere, are here forced to use a very different word: “world”.
In other instances, the problems posed are even more obvious, because it is explicitly stated that the aion has an end, and therefore cannot be eternal. Consider Jesus’ parable of the tares: “As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world [aiōnos]” (Matt 13:40; KJV). Of course, one cannot speak of the end of an eternity!